1. Field of the Invention
This invention concerns improvement of cylindrical coreless ms vibration alarm of the silent call type, by means of vibration.
2. Description of Related Art
In the past, coreless motors of this type have an eccentric weight W attached to a rotating shaft 11 that projects outside a housing 10, as shown in FIG. 5.
Such a coreless motor has a cylindrical external housing 10 that is reduced to a small-diameter cylinder at one end. The rotating shaft 11, one end of which projects outside the external housing 10 from the small diameter cylinder end, passes through the central axis of the external housing 10, and passes through and is supported by a bearing 12 fitted inside the small-diameter cylinder end, so that the rotating shaft 11 is free to rotate.
Moreover, a magnet 13 is fitted around and fixed to the outside of a bearing housing 14. This bearing housing 14 is fitted on the coaxial position of the rotating shaft 11, and holds a separate bearing 15 that is on the coaxial position of the rotating shaft 11. A cylindrical coil 16 is assembled to accommodate within the inside diameter the magnet 13, separated by a magnetic gap G. The coil 16 is held by a coil holder 17 that is mounted on the coaxial position of the rotating shaft 11 that extends beyond the bearing 15.
Beyond that, a commutator mechanism is assembled of a commutator element 18a mounted on the coil holder 17, and a brush 18c that is held by a brush holder 18b. An end cap 19 is attached, which acts to hold in place the end of the magnet 13 that is fitted around the outside of the bearing housing 14, and to hold in place the end of the coil 16 that is held on the coaxial position of the rotating shaft 11.
Because this coreless motor is made up primarily of metal parts, it is heavy, and because there are many parts, the assembly involves many processes, and requires much time. That is linked to high costs, and there is also a problem of precision because of the number of parts to be assembled.
The goals of this invention are to reduce weight by reducing the metal parts, and to reduce costs by reducing assembly processes and time by means of a smaller number of parts, thus providing a highly precise coreless motor with improved precision of assembly.
In the coreless motor of this invention, there is a cylindrical external housing with a through hole in a central position in the closed end. A molded resin body is molded into place through the through hole of the external housing; one end is a bearing that supports the rotating shaft, and it continues on the coaxial position of the rotating shaft to become a bearing housing that is fitted into place. The molded resin body is the base on which both the rotor and the stator are assembled.
Further, in the coreless motor of this invention, there are concave notches in the end of the bearing housing, and there is a hold-down collar that has on its inner diameter protrusions that mate with the notches in the bearing housing. The stator is assembled with the magnet held down by this hold-down collar that at the same time meshes the magnet with the periphery of the bearing housing.
Moreover, in the coreless motor of this invention, there is a bearing that has an oil reserve that lubricates the inner surface of the through hole through which the rotating shaft passes.